In general, a sample traveling stage is an equipment item used for loading, travel measuring, and/or processing an object (or sample, used for inspection equipment or precision processing equipment of semiconductors or FPDs to a desired location; and it is used for a laser displacement measuring system to analyze the displacement signal with the signal measured by the interference between the incident laser beam to the mirror and the reflected laser beam by the mirror.
For example, as illustrated in FIG. 1, sample traveling stage (100) has a main body part that includes X, Y slide (113, 114) guided by X, Y guide (111, 112) in a mutual crossing direction, sample table (116) mounted on the above Y slide (114) and moving sample (115), and the X, Y bar mirror attached to the above sample table (116) in a mutually vertical direction. A measuring part includes an interferometer (133) to diffuse the X, Y beam, which is output at laser head (131) after being mounted on the operating path of the above main body part and divided through beam divider (132), by the above X, Y bar mirror (117, 118), and X, Y receiver (134) so as to convert the interference signal, which is reflected by the above X, Y bar mirror (117, 118), into a displacement signal.
Accordingly, because the sample position measurement by sample traveling stage (100) has a structure measured by the interference between X, Y bar mirror (117, 118) fixed to the above sample table (116) and the laser beam reflected by the X, Y bar mirror (117, 118), the problem in which relative displacement between the above X, Y bar mirror (117, 118) and the above sample (115) must be maintained regularly, needs to be resolved previously in order to measure the correct position of the above sample (115).
However, sample table (116) of sample traveling stage (100) can be deformed due to the following reasons. For example, slide (113, 114) is subject to a processing error of guide part (111, 112) or an error in terms of linearity and flatness. Furthermore, in the case that ambient temperature changes, the deformation degree is different due to differences in the thermal expansion coefficient between slide (113, 114) and sample table (116), and, particularly, in cases where slide (113, 114) and sample table (116) are subject to connecting tools such as a bolt, problems relating to the deformation of slide (113, 114) occur as it is delivered to sample table (116).
These situations cause a deformation of mirror (118) and sample (115), and change the relative distance between the two during the usage process of sample traveling stage (100) as illustrated in FIG. 2, where sample table (116) is deformed due to the above reasons. These directly cause measuring errors and make the correct positioning of the sample difficult.
Furthermore, if the alignment of the laser beam is twisted due to tilt errors of mirror (118) caused by the deformation of sample table (116) when laser beam (135), output from the measuring part of sample traveling stage (100), enters the mirror, the interference between the incident beam and the reflected beam does not occur, and the measuring signal for displacement is lost. Losing the measuring signal at the displacement measuring system using laser beam (135) can be a serious problem insofar as it reduces control safety. Therefore, such instances should be prevented.
Referring to FIG. 3, U.S. Patent Application Publication No. 2003/0020225 describes a configuration in which deformation of slide (114) would not be imparted to sample table (116) by mounting three deformation preventing devices (150) having a motion free angle at the X, Y direction at the space between slide (114) and sample table (116).
U.S. Patent Application Publication No. 2003/0020225 additionally describes flexure mechanism (160) to restrict the motion in the X, Y direction in order to prevent the low strength in the X, Y direction of deformation preventing mechanism (150).
However, although U.S. Patent Application Publication No. 2003/0020225 describes flexure mechanism (160) as a deformation preventing mechanism reinforcement tool (150), it is difficult to compensate for the reduced strength in the X, Y direction. Furthermore, asymmetrical properties arise due to the asymmetrical structure when ambient temperature changes.
In addition, the height difference between sample (115) and slide (114) occurs due to the height of deformation preventing mechanism (150, 160). This causes a problem in terms of reduced stability because it forms a weight center in the drive unit and forms an offset between the drive unit operating point and the actual weight center.
Furthermore, as illustrated in FIG. 4, the configuration in which the deformation of slide (114) would not be delivered to sample table (116) is provided by configuring three buffering mechanisms (170) fixed with sample table (116) at the upper side of slide (114), and by permitting only a free angle toward the radius direction to become more distant from the center of the thermal expansion direction with the restriction of six free angles by the above buffering mechanism (170).
However, the above configuration has certain problems. For example, sample traveling stage (100) as illustrated in FIG. 4 has difficulties in terms of processing and assembly for buffering mechanism (170), and a height difference between sample table (116) and slide (114) occurs due to the height of buffering mechanism (170). This not only makes the weight center of the drive unit for sample traveling stage high, but also reduces control stability because this makes the offset between the point at which the drive force operates and the actual weight center.
For the precision equipment demanding super precision suitable for sample traveling stage (100), materials such as Invar or Zerodur, for the above slide (113, 114) and sample table (116) are used for a single body so as to resolve the above problems. However, this use has certain problems. For example, the cost of Invar or Zerodur is at least ten times that of aluminum, and processing costs also increase because of poor workability levels.